Art of cracking hydrocarbons



Patented Jan. 13, 1931 To S'INCLAIR REFINrNG'coM- PANY; or NEW YORK, Ng.Y., A ooRioRA'rIoN or MAINE ART or CRACKING nynRocAaeoivs i'.Application filed January 4, 1928. Serial No. 244,440.

Y This invention relates to improvements -in the operation of refluxcondensers .employed iny connectionivith `pressure stills for crack-gingheavier and higher boiling hydrocarbon '5 oils, such as gasoil, for theproduction yof lighter and lower boiling hydrocarbonoils,

such; as gasoline,` and gasoline-containing pressure distillates. In an,application filed 10, Serial No.` 208,741, 'which Patent NO..1,755,60-1,April-22,1930, there is described animproved method of operating suchreflux condensers, that method comprising the introduction of a lightoil refluxing mediun at a l number of points along they pathof vaportravel through thereflux condenser instead of within a closely,localized region, the proportion-of hght oil 2 introduced at cachotthese `points beingreginthe refluxY condenser and to distribute and tomake more uniform the heat transfer between heavier components ofthevapors and lighter components of the *liquids*y in the reflux condenser.One of the 1mpor tant advantages .of this method of operation isreduction for elimination ofrthe .tendoncy ofthe condensed heavierconstituents forming' the reflux condensate to carry back to thepressure still with them lighterpconystit'uents suitablel as componentslof` the desired product, With'corresponding reduction or elimination otlany tendency toward overcracking `of such lighter constituents.

As pointed outin this prior application, it `is lcommon practice in theoperation of pressure cracking stills to subject the vapors from thestillto some refluxing operation to 40 condense from the vapors forreturn .tothe still heavier constituents unsuitable as components of thedesired product but which by` further treatment will yield addltional jquantities of constituents suitable as components of the desiredproduct, one type of such refluxingoperation being carried out with theintroduction vinto direct' contact with the vapors from the pressurestill in a;

reflux condenser of a light oilwhichlargely oncompletely vaporizes atthe temperature n j tages.r: .For example, as commonly 20ulatedtodistribute and to make more uniy form the cooling andcondensation eliected and under the pressure prevailingkin the'refluxing operation. In another type of `re-;

fluxing operation commonly` employed,,rau1

oil to belsupplicd to t11`e 'pres'sure distilla1 t, tion, orfpart-'ofit, isintroducedinto directl coritaot-with the vapors from the pressure"still in a rei-lux' condenser, the Yvapors being j Y cooled f andtheheavierconstituents" con- July 27th, *1927,A

has matured into densed lby the consequent heatg"exchange Whilev therawy oil isnprehe'ated vvandfa/nyY lighter constituents ksuitable *ascomponents of, the desired product arefvaporized toy es-y cape withtheuncondensed vaporsfrom theing from the reflux condenserfandconsequent contaminationof the dist1llate is in-VV lvolved, and theamount-and the temperature of. raw oil so introduced into the refluxcondenserv are subjectto close limitations as otherwise the vapors inlthe refluxcondenserf are cooled too muchlor not enough.. Likel wise, if`additional .raw oil is rectly to tliepressure still, any lightconstitucnts itmay` contain'may be subjected tov over-cracking with the.same objectionable incidents lnvolved in operation. V

supplied dij .Over-cracking of light Y constituents entrained *1n refluxcondensate from the vapors subjectedjlo' the lrefluxi-ng 85 It has alsobeen proposedto combine these l y types of l reiluzzing tftoperations,.introducing raw oil at an ,intermediate point and`intro ducingsome-'lighthoilat af more remote point in the pathof vapor travelthrough thereflux condenser. The present invention-re,-

lates particularly to improvements in such operations, thatwis `toimprovements in the operation of'reflux condensers employed inconnection with pressure stills for. cracking hydrocarbon oils in-fvvhichrawroil is intro 'duced at au intermediateppoint'- and somelight oil at ajmoreiremote point in the path of vapor traveltherethrough.

duced at a number of points distributed along the subsequent path .ofvapor travel into a refiuxcondense'r in which the vapors from thepressure still are subjected to a refluxin operation. By introducing thelight oil re uxing medium, anvv oil vaporizing sub-j stantiallycompletelyin therefluxing operation, at aA number of distributed, pointsi composition and boiling range of the escapinstead of in a closelylocalized region extreme concentration of .the `cooling consequent to vaorization of the hght oil is avoided. us, a more uniform temperaturegradient cani be maintained along. the path of vapor travelthrough thereflux condenser- The raw oil1ntroduced into the reuxcondenserconsequently can be introduced at ,a point where it 'assistsfinmaintaining thefdesired' temperature gradient without involving eitherentrainmentfof o Y theqdesired productY in the oilmixture owing` Vfromthe reflux condenser to the pressure still kor entrainmentof heavier rawo'il constituents vin the vapors escapinv from the reflux condenser. Inany particu ar opi eration, an-increased amount'ofraw oil can beintroducedl into the refiuxing operation' simply .by introducing the rawoilat-a'point nearer in the path ofvapor travelto the inlet tothefreilux condenser, and similarly, rawoilsof higher temperature can beintroduced into the refluxing operation simply by introducing the-rawoil at a point -nearer in lthepath `of .vaportravel to thefinletnto" thereiux condenser` while maintaining the ing vapors as desired. In thiscombined operation, distribution of the introduction of," the light oilreiiuxing medium, is of special advanta c in providing accuracy ofcontrol', uniformity of operation, and in-fsecuring maximum ca acity.-In-one aspect the ntroduction o -rawoil at-a separate point or pointsin advance,l in the path of vapor travel, `of the several points otintroduction of' the-light oil reuxin medium is an extension of the`distribution of the introduced' Arefluxing' media,` actingfurther todistribute Referring to the drawing, the reflux condenser 1 is connectedto a'pressure cracking still by the vapor line 2 and the reilux returnhne 3. The tower is provided interiorly with bailies 4. Vapors from thestill enter the lower part of thetower through the line 2 and assupwardly through the tower back and' orth between the several bailies.

Vapore remaining uncondensed escape fromcondensed andl collected.Pressure in the still system may be maintained through the reflux towerand regulated, for example, by means of valve 6 in the va or connectionbetween the'reiux tower an the final condenser. Forthe production vofgasoline from'gas oil, for example, the'pr'essur'e in thesystem mayamountto'as vmuch as 100 poundsV per square inch, 150 pounds, 3003pounds or more. Raw oil `to\ be supplied to pressure still is introducedinto `the lower -l7part ofthe tower through 'the spray head li hterconstituents suitable ascomponents by'means of thel pum 1Stand. thevalved connection 9. Arrange` inthe upper'part' ofthe reflux tower, atpoints spaced a substantial distance along the path" olf-"vapor: travelrdefined by'thebaiiles, are three spraymeans of the pump 14. f A lightoil' which is. v'aporized` substantially completelyl 4under `theconditions prevailing in that zone ofthe tower above the spray head 7,for example,

a portion of the pressure distillate fromv the operation or an'oil ofcorresponding character, is" introduced through these spray heads into`the tower 'in contactV with' the va ors flowing upwardly through thetower.

s the 'hot vapors from the pressure still entering throughv line 2 passupwardly through vthe tower, the are firstcontacted with the raw oilintro uced through spray head 7. The vapors fromthe'pressure still arethereby partially cooled and the raw oil is,"in turn, heated bythey heatexchan re. Lighter constituents ofthe raw oil maya o be vaporized topass vupwardly.through the tower togetherw1th theV uncondensed vaporsfrom the pressure still. The unvaporlzed portion ofthe raw oil, together,withthe eavy condensed yconstituents ofthe vapors from the pressurestill,` pass downwardly throughthe i tower in. contact withv theascendinghot vapors. The vaplors from the pressure' still uncondensed byeat exchange with the rawoil, together with'such'li'ghter constituentsaswre vaporizedfrom the'raw' oil, flow on upwardl through the tower tobe further cooled an condensed by heat exf change with the light oilreluxing medium heads are connected to a introduced .through the sprayheads 10, 11 and 12. The resulting condensate flows downwardly throughthe tower over the bafdes in contact with the rising vapors, thiscontinued heat exchange further vaporizin -lighter constituents of thecondensate an condensing heavier constituents of the vapors.

It will be apparent that the invention provides for im roved uniformityof distribution of the eat exchange and consequent vaporization andcondensation along the path of vapor travel through the redux condenser,and this more uniform distribution of heat exchange assists inincreasing the capacity of the redux condenser as well as in improvingthe accuracy of the fractionation secured. Where either raw oil to besupplied to the cracking operation or a light oil reduxin medium isintroduced in a closely loca ized region there is a correspondingtendencyl toward condensation in that region of bot lighter and heavierconstituents of the vapors while both heavier and lighter constituentsremain uncondensed, althou h this tendency is less marked in the case oraw oil than of a light oil reduxing medium. By distributing theintroduction' of the light oil reduxing medium and the raw oil, actingas a reduxing medium, in accordance with this invention, however,condensation of heavier constituents without condensation of lighterconstituents is promoted while at the same time better opportunity isafforded for revaporization from condensate or vaporization from raw oilof any entrained lighter constituents. Entrainment of heavierconstituents in the vapors escaping from the reflux condenser is alsominimized by this distribution of the introduction of the refluxingmedium.

The oil mixture including heavier constituents condensed from the vaporsand the unvaporized raw oil flows from the lower end of the redux towerback to the pressure still through line 3. The return connection to theressure still ma include a pump or other orcing means or introducingthis oil mixture into the pressure still.

In carrying out the present invention, the

light oil reduxing medium supplied through spray heads 10, 11, and 12 inthe u per part of the redux tower may be distri uted for example,approximately equally through each of these spray heads, or a greaterroportion of the light oil reduxing me lum may be introduced through thespray head 11 than through spray heads 10 or 12 or a somewhat greaterproportion of the light oil reduxing medium may be through spray head 10than through 11 and in turn through 11 than through 12. The point orpoints at which raw oil is introduced into the redux tower is bestdetermined by the temperature and the amount introduced' of the raw oilso to be introduced. 'This point should be lower as the temperature oras the amount of raw oil to be introduced increases. y

In carryin out the present invention, the raw oil intro uced into theredux tower may be preheated, for example, by indirect heat exchangewith the vapors escaping from the redux tower or by indirect heatexchange with tar or residue discharged from the pressure still. In oneaspect, this invention enables raw oil so supplied to the pressuredistillation to be preheated to a higher temperature. In another aspect,b preheating the raw oil, this invention ena les a larger proportion ofthe raw oil to be supplied to the pressure distillationl through thereduxing operation. Light constituents of the raw oil suitable ascomponents of the desired product may thus be vaporized from the raw'oil before it is subjected to the cracking conditions maintained in theheatin zone in the pressure still, over-cracking o such raw oilconstituents thus being lavoided as well as over-cracking of similarlight constituents which might be entrained from the vapors from thepressure still.

I claim:

In reduxing operations employed in conjunction with the cracking ofhydrocarbon oils by distillation under pressure, the improvement whichcomprises passing the vapors from the` pressure distillation through aredux condenser introducing into the redux condenser vin direct contactvwith the vapors passing therethrough at an intermediate point in thepath of vapor travel raw oil to be supplied to the ressure distillation,introducing into the re ux condenser in direct contact withthe vaporspassing there- Y through at a plurality of points spaced a substantialdistance further along the path of vapor travel a light oil that isvaporized substantially completely under the conditions prevailing inthe redux condenser, and returning the oil mixture including condensateand unvaporized raw oil from the redux condenser to the pressuredistillation, whereby entrainment 1n the redux condensate of lightconstituents suitable as components of `1 the desired distillate isreduced.

In testimony whereof, I have subscribed my name.

. EUGENE C. HERTHEL.

